Lettuce line SV3673LD

ABSTRACT

The invention provides seed and plants of the lettuce line designated SV3673LD. The invention thus relates to the plants, seeds and tissue cultures of lettuce line SV3673LD, and to methods for producing a lettuce plant produced by crossing a plant of lettuce line SV3673LD with itself or with another lettuce plant, such as a plant of another line. The invention further relates to seeds and plants produced by such crossing. The invention further relates to parts of a plant of lettuce line SV3673LD, including the gametes of such plants.

FIELD OF THE INVENTION

The present invention relates to the field of plant breeding and, morespecifically, to the development of lettuce line SV3673LD.

BACKGROUND OF THE INVENTION

The goal of vegetable breeding is to combine various desirable traits ina single variety/hybrid. Such desirable traits may include greateryield, resistance to insects or pests, tolerance to heat and drought,better agronomic quality, higher nutritional value, growth rate andfruit properties.

Breeding techniques take advantage of a plant's method of pollination.There are two general methods of pollination: a plant self-pollinates ifpollen from one flower is transferred to the same or another flower ofthe same plant or plant variety. A plant cross-pollinates if pollencomes to it from a flower of a different plant variety.

Plants that have been self-pollinated and selected for type over manygenerations become homozygous at almost all gene loci and produce auniform population of true breeding progeny, a homozygous plant. A crossbetween two such homozygous plants of different varieties produces auniform population of hybrid plants that are heterozygous for many geneloci. Conversely, a cross of two plants each heterozygous at a number ofloci produces a population of hybrid plants that differ genetically andare not uniform. The resulting non-uniformity makes performanceunpredictable.

The development of uniform varieties requires the development ofhomozygous inbred plants, the crossing of these inbred plants, and theevaluation of the crosses. Pedigree breeding and recurrent selection areexamples of breeding methods that have been used to develop inbredplants from breeding populations. Those breeding methods combine thegenetic backgrounds from two or more plants or various other broad-basedsources into breeding pools from which new lines are developed byselfing and selection of desired phenotypes. The new lines are evaluatedto determine which of those have commercial potential.

SUMMARY OF THE INVENTION

In one aspect, the present invention provides a lettuce plant of theline designated SV3673LD. Also provided are lettuce plants having thephysiological and morphological characteristics of the lettuce linedesignated SV3673LD. Parts of the lettuce plant of the present inventionare also provided, for example, including pollen, an ovule, and a cellof the plant.

The invention also concerns seed of lettuce line SV3673LD. The lettuceseed of the invention may be provided as an essentially homogeneouspopulation of lettuce seed of the line designated SV3673LD. Essentiallyhomogeneous populations of seed are generally free from substantialnumbers of other seed. In certain embodiments of the invention, seed ofline SV3673LD may be provided forming at least about 97% of the totalseed, including at least about 98%, 99%, or more of the seed. Thepopulation of lettuce seed may be particularly defined as beingessentially free from hybrid seed. The seed population may be separatelygrown to provide an essentially homogeneous population of lettuce plantsdesignated SV3673LD.

In another aspect of the invention, a plant of lettuce line SV3673LDcomprising an added heritable trait is provided. The heritable trait maycomprise a genetic locus that is a dominant or recessive allele. In oneembodiment of the invention, a plant of lettuce line SV3673LD is definedas comprising a single locus conversion. In specific embodiments of theinvention, an added genetic locus confers one or more traits such as,for example, herbicide tolerance, insect resistance, disease resistance,and modified carbohydrate metabolism. The trait may be, for example,conferred by a naturally occurring gene introduced into the genome ofthe line by backcrossing, a natural or induced mutation, or a transgeneintroduced through genetic transformation techniques into the plant or aprogenitor of any previous generation thereof. When introduced throughtransformation, a genetic locus may comprise one or more transgenesintegrated at a single chromosomal location.

In another aspect of the invention, a tissue culture of regenerablecells of a plant of line SV3673LD is provided. The tissue culture willpreferably be capable of regenerating plants capable of expressing allof the physiological and morphological characteristics of the line, andof regenerating plants having substantially the same genotype as otherplants of the line. Examples of some of the physiological andmorphological characteristics of the line SV3673LD include those traitsset forth in the tables herein. The regenerable cells in such tissuecultures may be derived, for example, from embryos, meristems,cotyledons, pollen, leaves, anthers, roots, root tips, pistil, flower,seed and stalks. Still further, the present invention provides lettuceplants regenerated from a tissue culture of the invention, the plantshaving all the physiological and morphological characteristics of lineSV3673LD.

In yet another aspect of the invention, processes are provided forproducing lettuce seeds and plants, which processes generally comprisecrossing a first parent lettuce plant with a second parent lettuceplant, wherein at least one of the first or second parent lettuce plantsis a plant of the line designated SV3673LD. These processes may befurther exemplified as processes for preparing hybrid lettuce seed orplants, wherein a first lettuce plant is crossed with a second lettuceplant of a different, distinct line to provide a hybrid that has, as oneof its parents, the lettuce plant line SV3673LD. In these processes,crossing will result in the production of seed. The seed productionoccurs regardless of whether the seed is collected or not.

In one embodiment of the invention, the first step in “crossing”comprises planting seeds of a first and second parent lettuce plant,often in proximity so that pollination will occur for example, mediatedby insect vectors. Alternatively, pollen can be transferred manually.Where the plant is self-pollinated, pollination may occur without theneed for direct human intervention other than plant cultivation.

A second step may comprise cultivating or growing the seeds of first andsecond parent lettuce plants into plants that bear flowers. A third stepmay comprise preventing self-pollination of the plants, such as byemasculating the male portions of flowers, (i.e., treating ormanipulating the flowers to produce an emasculated parent lettuceplant). Self-incompatibility systems may also be used in some hybridcrops for the same purpose. Self-incompatible plants still shed viablepollen and can pollinate plants of other varieties but are incapable ofpollinating themselves or other plants of the same line.

A fourth step for a hybrid cross may comprise cross-pollination betweenthe first and second parent lettuce plants. Yet another step comprisesharvesting the seeds from at least one of the parent lettuce plants. Theharvested seed can be grown to produce a lettuce plant or hybrid lettuceplant.

The present invention also provides the lettuce seeds and plantsproduced by a process that comprises crossing a first parent lettuceplant with a second parent lettuce plant, wherein at least one of thefirst or second parent lettuce plants is a plant of the line designatedSV3673LD. In one embodiment of the invention, lettuce seed and plantsproduced by the process are first generation (F₁) hybrid lettuce seedand plants produced by crossing a plant in accordance with the inventionwith another, distinct plant. The present invention further contemplatesplant parts of such an F₁ hybrid lettuce plant, and methods of usethereof. Therefore, certain exemplary embodiments of the inventionprovide an F₁ hybrid lettuce plant and seed thereof.

In still yet another aspect of the invention, the genetic complement ofthe lettuce plant line designated SV3673LD is provided. The phrase“genetic complement” is used to refer to the aggregate of nucleotidesequences, the expression of which sequences defines the phenotype of,in the present case, a lettuce plant, or a cell or tissue of that plant.A genetic complement thus represents the genetic makeup of a cell,tissue or plant, and a hybrid genetic complement represents the geneticmake up of a hybrid cell, tissue or plant. The invention thus provideslettuce plant cells that have a genetic complement in accordance withthe lettuce plant cells disclosed herein, and plants, seeds and plantscontaining such cells.

Plant genetic complements may be assessed by genetic marker profiles,and by the expression of phenotypic traits that are characteristic ofthe expression of the genetic complement, e.g., isozyme typing profiles.It is understood that line SV3673LD or a first generation progenythereof could be identified by any of the many well known techniquessuch as, for example, Simple Sequence Length Polymorphisms (SSLPs)(Williams et al., Nucleic Acids Res., 1 8:6531-6535, 1990), RandomlyAmplified Polymorphic DNAs (RAPDs), DNA Amplification Fingerprinting(DAF), Sequence Characterized Amplified Regions (SCARs), ArbitraryPrimed Polymerase Chain Reaction (AP-PCR), Amplified Fragment LengthPolymorphisms (AFLPs) (EP 534 858, specifically incorporated herein byreference in its entirety), and Single Nucleotide Polymorphisms (SNPs)(Wang et al., Science, 280:1077-1082, 1998).

In still yet another aspect, the present invention provides hybridgenetic complements, as represented by lettuce plant cells, tissues,plants, and seeds, formed by the combination of a haploid geneticcomplement of a lettuce plant of the invention with a haploid geneticcomplement of a second lettuce plant, preferably, another, distinctlettuce plant. In another aspect, the present invention provides alettuce plant regenerated from a tissue culture that comprises a hybridgenetic complement of this invention.

In still yet another aspect, the invention provides a method ofdetermining the genotype of a plant of lettuce line SV3673LD comprisingdetecting in the genome of the plant at least a first polymorphism. Themethod may, in certain embodiments, comprise detecting a plurality ofpolymorphisms in the genome of the plant. The method may furthercomprise storing the results of the step of detecting the plurality ofpolymorphisms on a computer readable medium. The invention furtherprovides a computer readable medium produced by such a method.

In still yet another aspect, the present invention provides a method ofproducing a plant derived from line SV3673LD, the method comprising thesteps of: (a) preparing a progeny plant derived from line SV3673LD,wherein said preparing comprises crossing a plant of the line SV3673LDwith a second plant; and (b) crossing the progeny plant with itself or asecond plant to produce a seed of a progeny plant of a subsequentgeneration. In further embodiments, the method may additionallycomprise: (c) growing a progeny plant of a subsequent generation fromsaid seed of a progeny plant of a subsequent generation and crossing theprogeny plant of a subsequent generation with itself or a second plant;and repeating the steps for an additional 3-10 generations to produce aplant derived from line SV3673LD. The plant derived from line SV3673LDmay be an inbred line, and the aforementioned repeated crossing stepsmay be defined as comprising sufficient inbreeding to produce the inbredline. In the method, it may be desirable to select particular plantsresulting from step (c) for continued crossing according to steps (b)and (c). By selecting plants having one or more desirable traits, aplant derived from line SV3673LD is obtained which possesses some of thedesirable traits of the line as well as potentially other selectedtraits.

In certain embodiments, the present invention provides a method ofproducing lettuce comprising: (a) obtaining a plant of lettuce lineSV3673LD, wherein the plant has been cultivated to maturity, and (b)collecting lettuce from the plant.

Any embodiment discussed herein with respect to one aspect of theinvention applies to other aspects of the invention as well, unlessspecifically noted.

The term “about” is used to indicate that a value includes the standarddeviation of error for the device or method being employed to determinethe value. The use of the term “or” in the claims is used to mean“and/or” unless explicitly indicated to refer to alternatives only orthe alternatives are mutually exclusive, although the disclosuresupports a definition that refers to only alternatives and to “and/or.”When used in conjunction with the word “comprising” or other openlanguage in the claims, the words “a” and “an” denote “one or more,”unless specifically noted. The terms “comprise,” “have” and “include”are open-ended linking verbs. Any forms or tenses of one or more ofthese verbs, such as “comprises,” “comprising,” “has,” “having,”“includes” and “including,” are also open-ended. For example, any methodthat “comprises,” “has” or “includes” one or more steps is not limitedto possessing only those one or more steps and also covers otherunlisted steps. Similarly, any plant that “comprises,” “has” or“includes” one or more traits is not limited to possessing only thoseone or more traits and covers other unlisted traits.

Other objects, features and advantages of the present invention willbecome apparent from the following detailed description. It should beunderstood, however, that the detailed description and any specificexamples provided, while indicating specific embodiments of theinvention, are given by way of illustration only, since various changesand modifications within the spirit and scope of the invention willbecome apparent to those skilled in the art from this detaileddescription.

DETAILED DESCRIPTION OF THE INVENTION

The invention provides methods and compositions relating to plants,seeds and derivatives of lettuce line SV3673LD. This line showsuniformity and stability within the limits of environmental influencefor the traits described hereinafter. Lettuce line SV3673LD providessufficient seed yield. By crossing with a distinct second plant, uniformF1 hybrid progeny can be obtained.

Lettuce line SV3673LD is a vigorous iceberg lettuce cultivar adapted forspring production in desert areas of California and Arizona. The optimalsowing dates for this variety are from 15 November to 5 December in bothImperial County, CA and in Yuma County, AZ. Cv. SV3673LD was selectedfor medium to large size with good weight and increased resistance totipburn compared to the most similar commercial cultivar, cv. Coyote.

A. PHYSIOLOGICAL AND MORPHOLOGICAL CHARACTERISTICS OF LETTUCE LINESV3673LD

In accordance with one aspect of the present invention, there isprovided a plant having the physiological and morphologicalcharacteristics of lettuce line SV3673LD. A description of thephysiological and morphological characteristics of lettuce line SV3673LDis presented in Table 1.

TABLE 1 Physiological and Morphological Characteristics of Line SV3673LDComparison Comparison Variety- Variety- Characteristic SV3673LD CoyoteVanguard 1. Type Vanguard Group Vanguard Vanguard Group Group 2. Seedcolor black (US: Grey black black Brown) [TG: Kagraner Sommer] lightdormancy light not required light not light not required required heatdormancy susceptible susceptible susceptible seedling: anthocyaninabsent (Verpia) coloration seedling: size of cotyledon medium (Expresse)(fully developed) seedling: shape of medium elliptic cotyledon(Frisette) 3. Shape shape of cotyledons intermediate intermediateintermediate shape of fourth leaf elongated elongated elongatedlength/width index of fourth 1.74 1.79 1.66 leaf apical margin(cotyledon to crenate/gnawed finely dentate finely dentate 4^(th) leafstage) basal margin (cotyledon to coarsely dentate coarsely coarsely4^(th) leaf stage) dentate dentate undulation (cotyledon to 4^(th) flatslight slight leaf stage green color (cotyledon to 4^(th) medium greenmedium green medium green leaf stage) anthocyanin distribution absentabsent absent (cotyledon to 4^(th) leaf stage) rolling (cotyledon to4^(th) leaf absent absent absent stage) cupping (cotyledon to 4^(th)uncupped uncupped uncupped leaf stage) reflexing (cotyledon to 4^(th)none none none leaf stage) leaf: attitude at 10-12 leaf semi-erect(Great stage Lakes 118, Soraya leaf blade: division at 10-12 entire(Fiorella, leaf stage Sunrise) 4. Leaf blade incisions of margin onabsent (Verpia) apical part depth of incisions on absent/shallow (US:moderate/ moderate/ margin on apical part Dark Green Boston) mediummedium (harvest mature outer [TG: Pentared, leaves) Unicum] density ofincisions on sparse (Maravilla de margin on apical part Verano) type ofincisions on apical sinuate (Gloire du part Dauphiné) venationflabellate (Gloire du Dauphiné, Locarno, Monet) mature leaves:indentation crenate (Vanguard) crenate crenate finest divisions of themargin (harvest mature outer leaves) degree of undulation ofmoderate/medium moderate/ moderate/ apical margin (harvest (US:Vanguard) medium medium mature outer leaves) [TG: Noisette, Pentared]green color (harvest mature dark green (Vanguard) dark green dark greenouter leaves) leaf: hue of green color of absent (Donatello, outerleaves Verpia) leaf: intensity of color of medium outer leaves leaf:anthocyanin coloration absent [TG: Fiorella, Sunrise] leaf: anthocyaninabsent absent absent distribution (harvest mature outer leaves) leaf:size large large large leaf: glossiness of upper moderate/mediumdull/weak dull/weak side (harvest mature outer (US: Salinas) [TG:leaves) Feria, Sunrise] leaf: blistering (harvest absent/slight or verymoderate/ weak mature outer leaves) weak medium (US: Salinas) [TG:Donia, Frillblond] leaf: size of blisters medium (Dustin, Sunrise) leaf:thickness (harvest thick (Frisée de thick thick mature outer leaves)Beauregard) leaf: trichomes (harvest present (spiny) absent absentmature outer leaves) leaf: attitude at harvest horizontal (Chambery,maturity (outer leaves from Divina) head lettuce or adult leaves fromcutting and stem lettuce) leaf: shape transverse broad elliptic(Commodore, Fiorella) leaf: shape of tip rounded (Blonde Maraichere,Maserati 5. Plant spread of frame leaves 20.4 cm 22.3 cm 20.7 cmdiameter large (Great Lakes 659, Musette) height (flowering plant) tall(Danilla, Hilde II) intensity of fasciation absent (Calmar, (floweringplant) Romance) head formation closed head/ overlapping (Kelvin,Sunrise) varieties with closed head strong (Master, Minas) formationonly: head: degree of overlapping of upper part of plant head diameter(market 17.0 cm 18.6 cm 15.3 cm trimmed with single cap leaf) head shapespherical spherical spherical head shape in longitudinal circular (PassePartout, section Verpia) head size (class) large (Great Lakes very largelarge 659, Musette) heads per carton 24 24 24 head weight 983 gms 830gms 901 gms head firmness/density firm/dense (Hilde II, medium firmKelvin) 6. Butt shape rounded rounded rounded midrib moderately raisedmoderately moderately raised raised 7. Core diameter at base of head 38mm 39 mm 37 mm ratio of head diameter/core 4.5 4.8 4.6 diameter coreheight from base of 45 mm 50 mm 44 mm head to apex 8. Bolting firstwater date 23 Apr. 2013 number of days from first 97 88 80 water date toseed stalk emergence (summer conditions) bolting class medium mediummedium time of beginning of bolting medium (Carelia) under long dayconditions height of mature seed stalk 145 cm 154 cm 147 cm spread ofbolter plant (at 38 cm 39 cm 37 cm widest point) bolter leaves curvedcurved curved margin dentate dentate dentate color medium green mediumgreen medium green bolter habit: terminal absent absent absentinflorescence bolter habit: lateral shoots present present presentbolter habit: basal side absent absent absent shoots axillary sproutingabsent or very weak (Valmaine) time of harvest maturity medium (Newton)9. Maturity earliness of harvest-mature Spring: 119 days Spring: 122Spring: 118 head formation days days (number of days = first water dateto harvest) planting date(s) and Fall: 15 November to 5 location(s)December Imperial Co., CA Yuma Co., AZ 10. Adaptation: primary regionsof adaptation (tested and proven adapted) Southwest (CA and/or AZadapted desert) West Coast not tested Northeast not tested North Centralnot tested Southeast not tested Spring adapted Imperial Co., CA YumaCo., AZ Summer not adapted Fall not adapted Winter not adaptedgreenhouse not tested soil type mineral 11. Viral Diseases big veinsusceptible susceptible susceptible lettuce mosaic susceptiblesusceptible susceptible resistance to lettuce mosaic absent (Hilde II,virus (LMV) Strain Ls1 Salvina) 12. Fungal Diseases downy mildew races:all susceptible susceptible susceptible powdery mildew susceptiblesusceptible susceptible sclerotinia drop susceptible susceptiblesusceptible Botrytis (grey mold) susceptible susceptible susceptiblebacterial leaf spot susceptible susceptible susceptible 13. Insectslettuce aphid susceptible susceptible susceptible 14. Physiologicalstresses tipburn moderately resistant/ susceptible susceptiblesusceptible heat moderately resistant/ susceptible susceptiblesusceptible cold resistant resistant moderately resistant/ susceptible*These are typical values. Values may vary due to environment. Othervalues that are substantially equivalent are also within the scope ofthe invention.

B. BREEDING LETTUCE LINE SV3673LD

One aspect of the current invention concerns methods for crossing thelettuce line SV3673LD with itself or a second plant and the seeds andplants produced by such methods. These methods can be used forpropagation of line SV3673LD, or can be used to produce hybrid lettuceseeds and the plants grown therefrom. Hybrid seeds are produced bycrossing line SV3673LD with second lettuce parent line.

The development of new varieties using one or more starting varieties iswell known in the art. In accordance with the invention, novel varietiesmay be created by crossing line SV3673LD followed by multiplegenerations of breeding according to such well known methods. Newvarieties may be created by crossing with any second plant. In selectingsuch a second plant to cross for the purpose of developing novel lines,it may be desired to choose those plants which either themselves exhibitone or more selected desirable characteristics or which exhibit thedesired characteristic(s) when in hybrid combination. Once initialcrosses have been made, inbreeding and selection take place to producenew varieties. For development of a uniform line, often five or moregenerations of selfing and selection are involved.

Uniform lines of new varieties may also be developed by way ofdouble-haploids. This technique allows the creation of true breedinglines without the need for multiple generations of selfing andselection. In this manner true breeding lines can be produced in aslittle as one generation. Haploid embryos may be produced frommicrospores, pollen, anther cultures, or ovary cultures. The haploidembryos may then be doubled autonomously, or by chemical treatments(e.g. colchicine treatment). Alternatively, haploid embryos may be growninto haploid plants and treated to induce chromosome doubling. In eithercase, fertile homozygous plants are obtained. In accordance with theinvention, any of such techniques may be used in connection with lineSV3673LD and progeny thereof to achieve a homozygous line.

New varieties may be created, for example, by crossing line SV3673LDwith any second plant and selection of progeny in various generationsand/or by doubled haploid technology. In choosing a second plant tocross for the purpose of developing novel lines, it may be desired tochoose those plants which either themselves exhibit one or more selecteddesirable characteristics or which exhibit the desired characteristic(s)in progeny. After one or more lines are crossed, true-breeding lines maybe developed.

Backcrossing can also be used to improve an inbred plant. Backcrossingtransfers a specific desirable trait from one inbred or non-inbredsource to an inbred that lacks that trait. This can be accomplished, forexample, by first crossing a superior inbred (A) (recurrent parent) to adonor inbred (non-recurrent parent), which carries the appropriate locusor loci for the trait in question. The progeny of this cross are thenmated back to the superior recurrent parent (A) followed by selection inthe resultant progeny for the desired trait to be transferred from thenon-recurrent parent. After five or more backcross generations withselection for the desired trait, the progeny are heterozygous for locicontrolling the characteristic being transferred, but are like thesuperior parent for most or almost all other loci. The last backcrossgeneration would be selfed to give pure breeding progeny for the traitbeing transferred.

The line of the present invention is particularly well suited for thedevelopment of new lines based on the elite nature of the geneticbackground of the line. In selecting a second plant to cross withSV3673LD for the purpose of developing novel lettuce lines, it willtypically be preferred to choose those plants which either themselvesexhibit one or more selected desirable characteristics or which exhibitthe desired characteristic(s) when in hybrid combination.

C. PERFORMANCE CHARACTERISTICS

As described above, line SV3673LD exhibits desirable performance traits.The results of an analysis of such traits are presented below.

In replicated field trials, heads of cv. SV3673LD were consistentlysmaller in diameter (17.0 cm vs. 18.6 cm), yet heavier in weight (983 gvs. 830 g), and had a lower incidence of tipburn symptoms (0.1 vs. 5.0per head) when compared to cv. Coyote, respectively (Table 2). Aplausible reason for the lower average head weight of cv. Coyote wouldbe its inconsistent heading ability and decreased fitness often observedduring the late March harvest period, while cv. SV3673LD was geneticallybetter adapted, able to maintain a superior performance with size andweight at the required market standard.

The data presented here are statistically different at the 95%confidence level, exhibiting a range of means for head diameter from16.9 cm to 17.1 cm for cv. SV3673LD and from 18.2 cm to 18.9 cm for cv.Coyote, a range of means for head weight from 975.4 g to 982.1 g for cv.SV3673LD and from 817.1 g to 842.4 g for cv. Coyote, and a range ofmeans for tipburn incidence from 0.74 to 0.76 lesions per head for cv.SV3673LD and from 4.64 to 5.16 lesions per head for cv. Coyote,respectively. Therefore, these data for head diameter, head weight, andtipburn incidence illustrate that cv. SV3673LD was significantlydifferent than its most similar variety, cv. Coyote, in field trialsconducted in 2012 and 2013.

TABLE 2 Evaluation of cv. SV3673LD and the most similar cultivar, cv.Coyote, for characters. Head Head Tipburn Trial No Cultivar Rep No.Diameter^(a) Weight^(b) Incidence^(c) Trial 1: cv.SV3673LD: Rep. 1 16.8± 0.4 1051 ± 15.4  0.1 ± 0.07 Evaluated Rep. 2 17.2 ± 0.4 979 ± 14.8 0.2± 0.07 21 Mar 2012 Yuma, AZ Average: 17.0 ± 0.4 1023 ± 15.1  0.2 ± 0.07cv. Coyote: Rep. 1 18.3 ± 1.7 844 ± 59.4 5.2 ± 0.17 Rep. 2 18.7 ± 1.7720 ± 57.8 5.9 ± 0.19 Average: 18.5 ± 1.7 782 ± 58.6 5.6 ± 0.18 Trial 2:cv. SV3673LD: Rep. 1 17.3 ± 0.4 949 ± 14.4 0.0 ± 0.0  Evaluated Rep. 216.7 ± 0.3 936 ± 15.1 0.0 ± 0.0  26 Mar 2013 Yuma, AZ Average: 17.0 ±0.4 943 ± 14.8 0.0 ± 0.0  cv. Coyote: Rep. 1 18.9 ± 1.9 891 ± 53.2 4.4 ±0.14 Rep. 2 18.3 ± 1.6 864 ± 55.5 4.1 ± 0.12 Average: 18.6 ± 1.8 878 ±54.4 4.3 ± 0.13 cv. SV3673LD 16.9 to 17.1 975.4 to 982.1 0.74 to 0.76cv. Coyote 18.2 to 18.9 817.1 to 842.4 4.64 to 5.16 Range of variationamong means of statistically significant differences at the 95% levelusing the confidence interval [CI = mean ± (SDXSE)]: ^(a)Mean headdiameter using two sowing dates of 20 plants per replication in cm ±standard deviation. ^(b)Mean head weight using two sowing dates of 20plants per replication in grams ± standard deviation. ^(c)Mean tipburnincidence (number of lesions per head) using two sowing dates of 20plants per replication ± standard deviation.

D. FURTHER EMBODIMENTS OF THE INVENTION

In specific embodiments, the invention provides plants modified toinclude at least a first desired heritable trait. Such plants may, inone embodiment, be developed by a plant breeding technique calledbackcrossing, wherein essentially all of the desired morphological andphysiological characteristics of a variety are recovered in addition toa genetic locus transferred into the plant via the backcrossingtechnique. The terms converted plant or single locus converted plant asused herein refers to those lettuce plants which are developed by aplant breeding technique called backcrossing, wherein essentially all ofthe desired morphological and physiological characteristics of a varietyare recovered in addition to the single locus transferred into thevariety via the backcrossing technique. By essentially all of themorphological and physiological characteristics, it is meant that thecharacteristics of a plant are recovered that are otherwise present whencompared in the same environment, other than an occasional variant traitthat might arise during backcrossing or direct introduction of atransgene. It is understood that a locus introduced by backcrossing mayor may not be transgenic in origin, and thus the term backcrossingspecifically includes backcrossing to introduce loci that were createdby genetic transformation.

Backcrossing methods can be used with the present invention to improveor introduce a characteristic into the present variety. The parentallettuce plant which contributes the locus for the desired characteristicis termed the nonrecurrent or donor parent. This terminology refers tothe fact that the nonrecurrent parent is used one time in the backcrossprotocol and therefore does not recur. The parental lettuce plant towhich the locus or loci from the nonrecurrent parent are transferred isknown as the recurrent parent as it is used for several rounds in thebackcrossing protocol.

In a typical backcross protocol, the original variety of interest(recurrent parent) is crossed to a second variety (nonrecurrent parent)that carries the single locus of interest to be transferred. Theresulting progeny from this cross are then crossed again to therecurrent parent and the process is repeated until a lettuce plant isobtained wherein essentially all of the desired morphological andphysiological characteristics of the recurrent parent are recovered inthe converted plant, in addition to the single transferred locus fromthe nonrecurrent parent.

The selection of a suitable recurrent parent is an important step for asuccessful backcrossing procedure. The goal of a backcross protocol isto alter or substitute a single trait or characteristic in the originalvariety. To accomplish this, a single locus of the recurrent variety ismodified or substituted with the desired locus from the nonrecurrentparent, while retaining essentially all of the rest of the desiredgenetic, and therefore the desired physiological and morphologicalconstitution of the original variety. The choice of the particularnonrecurrent parent will depend on the purpose of the backcross; one ofthe major purposes is to add some commercially desirable trait to theplant. The exact backcrossing protocol will depend on the characteristicor trait being altered to determine an appropriate testing protocol.Although backcrossing methods are simplified when the characteristicbeing transferred is a dominant allele, a recessive allele may also betransferred. In this instance it may be necessary to introduce a test ofthe progeny to determine if the desired characteristic has beensuccessfully transferred.

In one embodiment, progeny lettuce plants of a backcross in whichSV3673LD is the recurrent parent comprise (i) the desired trait from thenon-recurrent parent and (ii) all of the physiological and morphologicalcharacteristics of lettuce line SV3673LD as determined at the 5%significance level when grown in the same environmental conditions.

Lettuce varieties can also be developed from more than two parents. Thetechnique, known as modified backcrossing, uses different recurrentparents during the backcrossing. Modified backcrossing may be used toreplace the original recurrent parent with a variety having certain moredesirable characteristics or multiple parents may be used to obtaindifferent desirable characteristics from each.

With the development of molecular markers associated with particulartraits, it is possible to add additional traits into an established germline, such as represented here, with the end result being substantiallythe same base germplasm with the addition of a new trait or traits.Molecular breeding, as described in Moose and Mumm, 2008 (PlantPhysiology, 147: 969-977), for example, and elsewhere, provides amechanism for integrating single or multiple traits or QTL into an eliteline. This molecular breeding-facilitated movement of a trait or traitsinto an elite line may encompass incorporation of a particular genomicfragment associated with a particular trait of interest into the eliteline by the mechanism of identification of the integrated genomicfragment with the use of flanking or associated marker assays. In theembodiment represented here, one, two, three or four genomic loci, forexample, may be integrated into an elite line via this methodology. Whenthis elite line containing the additional loci is further crossed withanother parental elite line to produce hybrid offspring, it is possibleto then incorporate at least eight separate additional loci into thehybrid. These additional loci may confer, for example, such traits as adisease resistance or a fruit quality trait. In one embodiment, eachlocus may confer a separate trait. In another embodiment, loci may needto be homozygous and exist in each parent line to confer a trait in thehybrid. In yet another embodiment, multiple loci may be combined toconfer a single robust phenotype of a desired trait.

Many single locus traits have been identified that are not regularlyselected for in the development of a new inbred but that can be improvedby backcrossing techniques. Single locus traits may or may not betransgenic; examples of these traits include, but are not limited to,male sterility, herbicide resistance, resistance to bacterial, fungal,or viral disease, insect resistance, restoration of male fertility,modified fatty acid or carbohydrate metabolism, and enhanced nutritionalquality. These comprise genes generally inherited through the nucleus.

Direct selection may be applied where the single locus acts as adominant trait. An example of a dominant trait is the downy mildewresistance trait. For this selection process, the progeny of the initialcross are sprayed with downy mildew spores prior to the backcrossing.The spraying eliminates any plants which do not have the desired downymildew resistance characteristic, and only those plants which have thedowny mildew resistance gene are used in the subsequent backcross. Thisprocess is then repeated for all additional backcross generations.

Selection of lettuce plants for breeding is not necessarily dependent onthe phenotype of a plant and instead can be based on geneticinvestigations. For example, one can utilize a suitable genetic markerwhich is closely genetically linked to a trait of interest. One of thesemarkers can be used to identify the presence or absence of a trait inthe offspring of a particular cross, and can be used in selection ofprogeny for continued breeding. This technique is commonly referred toas marker assisted selection. Any other type of genetic marker or otherassay which is able to identify the relative presence or absence of atrait of interest in a plant can also be useful for breeding purposes.Procedures for marker assisted selection applicable to the breeding oflettuce are well known in the art. Such methods will be of particularutility in the case of recessive traits and variable phenotypes, orwhere conventional assays may be more expensive, time consuming orotherwise disadvantageous. Types of genetic markers which could be usedin accordance with the invention include, but are not necessarilylimited to, Simple Sequence Length Polymorphisms (SSLPs) (Williams etal., Nucleic Acids Res., 1 8:6531-6535, 1990), Randomly AmplifiedPolymorphic DNAs (RAPDs), DNA Amplification Fingerprinting (DAF),Sequence Characterized Amplified Regions (SCARs), Arbitrary PrimedPolymerase Chain Reaction (AP-PCR), Amplified Fragment LengthPolymorphisms (AFLPs) (EP 534 858, specifically incorporated herein byreference in its entirety), and Single Nucleotide Polymorphisms (SNPs)(Wang et al., Science, 280:1077-1082, 1998).

E. PLANTS DERIVED FROM LETTUCE LINE SV3673LD BY GENETIC ENGINEERING

Many useful traits that can be introduced by backcrossing, as well asdirectly into a plant, are those which are introduced by genetictransformation techniques. Genetic transformation may therefore be usedto insert a selected transgene into the lettuce line of the invention ormay, alternatively, be used for the preparation of transgenes which canbe introduced by backcrossing. Methods for the transformation of plants,including lettuce, are well known to those of skill in the art.

Vectors used for the transformation of lettuce cells are not limited solong as the vector can express an inserted DNA in the cells. Forexample, vectors comprising promoters for constitutive gene expressionin lettuce cells (e.g., cauliflower mosaic virus 35S promoter) andpromoters inducible by exogenous stimuli can be used. Examples ofsuitable vectors include pBI binary vector. The “lettuce cell” intowhich the vector is to be introduced includes various forms of lettucecells, such as cultured cell suspensions, protoplasts, leaf sections,and callus.

A vector can be introduced into lettuce cells by known methods, such asthe polyethylene glycol method, polycation method, electroporation,Agrobacterium-mediated transfer, particle bombardment and direct DNAuptake by protoplasts. See, e.g., Pang et al. (The Plant J., 9, 899-909,1996).

To effect transformation by electroporation, one may employ eitherfriable tissues, such as a suspension culture of cells or embryogeniccallus or alternatively one may transform immature embryos or otherorganized tissue directly. In this technique, one would partiallydegrade the cell walls of the chosen cells by exposing them topectin-degrading enzymes (pectolyases) or mechanically wound tissues ina controlled manner. An example of electroporation of lettuceprotoplasts is presented in Chupeau et al. (Bio/Tech., 7:503-508, 1989).

A particularly efficient method for delivering transforming DNA segmentsto plant cells is microprojectile bombardment. In this method, particlesare coated with nucleic acids and delivered into cells by a propellingforce. Exemplary particles include those comprised of tungsten,platinum, and preferably, gold. For the bombardment, cells in suspensionare concentrated on filters or solid culture medium. Alternatively,immature embryos or other target cells may be arranged on solid culturemedium. The cells to be bombarded are positioned at an appropriatedistance below the macroprojectile stopping plate.

An illustrative embodiment of a method for delivering DNA into plantcells by acceleration is the Biolistics Particle Delivery System, whichcan be used to propel particles coated with DNA or cells through ascreen, such as a stainless steel or Nytex screen, onto a surfacecovered with target lettuce cells. The screen disperses the particles sothat they are not delivered to the recipient cells in large aggregates.It is believed that a screen intervening between the projectileapparatus and the cells to be bombarded reduces the size of projectilesaggregate and may contribute to a higher frequency of transformation byreducing the damage inflicted on the recipient cells by projectiles thatare too large.

Microprojectile bombardment techniques are widely applicable, and may beused to transform virtually any plant species. Examples involvingmicroprojectile bombardment transformation with lettuce can be found in,for example, Elliott et al. (Plant Cell Rep., 18:707-714, 2004) andMolinier et al. (Plant Cell Rep., 21:251-256, 2002).

Agrobacterium-mediated transfer is another widely applicable system forintroducing gene loci into plant cells. An advantage of the technique isthat DNA can be introduced into whole plant tissues, thereby bypassingthe need for regeneration of an intact plant from a protoplast. ModernAgrobacterium transformation vectors are capable of replication in E.coli as well as Agrobacterium, allowing for convenient manipulations(Klee et al., Bio-Technology, 3(7):637-642, 1985). Moreover, recenttechnological advances in vectors for Agrobacterium-mediated genetransfer have improved the arrangement of genes and restriction sites inthe vectors to facilitate the construction of vectors capable ofexpressing various polypeptide coding genes. The vectors described haveconvenient multi-linker regions flanked by a promoter and apolyadenylation site for direct expression of inserted polypeptidecoding genes. Additionally, Agrobacterium containing both armed anddisarmed Ti genes can be used for transformation.

In those plant strains where Agrobacterium-mediated transformation isefficient, it is the method of choice because of the facile and definednature of the gene locus transfer. The use of Agrobacterium-mediatedplant integrating vectors to introduce DNA into plant cells is wellknown in the art (Fraley et al., Bio/Technology, 3:629-635, 1985; U.S.Pat. No. 5,563,055). For example, U.S. Pat. No. 5,349,124 describes amethod of transforming lettuce plant cells using Agrobacterium-mediatedtransformation. By inserting a chimeric gene having a DNA codingsequence encoding for the full-length B.t. toxin protein that expressesa protein toxic toward Lepidopteran larvae, this methodology resulted inlettuce having resistance to such insects.

Transformation of plant protoplasts also can be achieved using methodsbased on calcium phosphate precipitation, polyethylene glycol treatment,electroporation, and combinations of these treatments (see, e.g.,Potrykus et al., Mol. Gen. Genet., 199:183-188, 1985; Omirulleh et al.,Plant Mol. Biol., 21(3):415-428, 1993; Fromm et al., Nature,312:791-793, 1986; Uchimiya et al., Mol. Gen. Genet., 204:204, 1986;Marcotte et al., Nature, 335:454, 1988). Transformation of plants andexpression of foreign genetic elements is exemplified in Choi et al.(Plant Cell Rep., 13: 344-348, 1994) and Ellul et al. (Theor. Appl.Genet., 107:462-469, 2003).

A number of promoters have utility for plant gene expression for anygene of interest including but not limited to selectable markers,scoreable markers, genes for pest tolerance, disease resistance,nutritional enhancements and any other gene of agronomic interest.Examples of constitutive promoters useful for lettuce plant geneexpression include, but are not limited to, the cauliflower mosaic virus(CaMV) P-35S promoter, which confers constitutive, high-level expressionin most plant tissues (see, e.g., Odel et al., Nature, 313:810, 1985),including monocots (see, e.g., Dekeyser et al., Plant Cell, 2:591, 1990;Terada and Shimamoto, Mol. Gen. Genet., 220:389, 1990); a tandemlyduplicated version of the CaMV 35S promoter, the enhanced 35S promoter(P-e35S) the nopaline synthase promoter (An et al., Plant Physiol.,88:547, 1988), the octopine synthase promoter (Fromm et al., Plant Cell,1:977, 1989); and the figwort mosaic virus (P-FMV) promoter as describedin U.S. Pat. No. 5,378,619 and an enhanced version of the FMV promoter(P-eFMV) where the promoter sequence of P-FMV is duplicated in tandem,the cauliflower mosaic virus 19S promoter, a sugarcane bacilliform viruspromoter, a commelina yellow mottle virus promoter, and other plant DNAvirus promoters known to express in plant cells.

A variety of plant gene promoters that are regulated in response toenvironmental, hormonal, chemical, and/or developmental signals can beused for expression of an operably linked gene in plant cells, includingpromoters regulated by (1) heat (Callis et al., Plant Physiol., 88:965,1988), (2) light (e.g., pea rbcS-3A promoter, Kuhlemeier et al., PlantCell, 1:471, 1989; maize rbcS promoter, Schaffner and Sheen, Plant Cell,3:997, 1991; or chlorophyll a/b-binding protein promoter, Simpson etal., EMBO J., 4:2723, 1985), (3) hormones, such as abscisic acid(Marcotte et al., Plant Cell, 1:969, 1989), (4) wounding (e.g., wunl,Siebertz et al., Plant Cell, 1:961, 1989); or (5) chemicals such asmethyl jasmonate, salicylic acid, or Safener. It may also beadvantageous to employ organ-specific promoters (e.g., Roshal et al.,EMBO J., 6:1155, 1987; Schernthaner et al., EMBO J., 7:1249, 1988;Bustos et al., Plant Cell, 1:839, 1989).

Exemplary nucleic acids which may be introduced to the lettuce lines ofthis invention include, for example, DNA sequences or genes from anotherspecies, or even genes or sequences which originate with or are presentin the same species, but are incorporated into recipient cells bygenetic engineering methods rather than classical reproduction orbreeding techniques. However, the term “exogenous” is also intended torefer to genes that are not normally present in the cell beingtransformed, or perhaps simply not present in the form, structure, etc.,as found in the transforming DNA segment or gene, or genes which arenormally present and that one desires to express in a manner thatdiffers from the natural expression pattern, e.g., to over-express.Thus, the term “exogenous” gene or DNA is intended to refer to any geneor DNA segment that is introduced into a recipient cell, regardless ofwhether a similar gene may already be present in such a cell. The typeof DNA included in the exogenous DNA can include DNA which is alreadypresent in the plant cell, DNA from another plant, DNA from a differentorganism, or a DNA generated externally, such as a DNA sequencecontaining an antisense message of a gene, or a DNA sequence encoding asynthetic or modified version of a gene.

Many hundreds if not thousands of different genes are known and couldpotentially be introduced into a lettuce plant according to theinvention. Non-limiting examples of particular genes and correspondingphenotypes one may choose to introduce into a lettuce plant include oneor more genes for insect tolerance, such as a Bacillus thuringiensis(B.t.) gene, pest tolerance such as genes for fungal disease control,herbicide tolerance such as genes conferring glyphosate tolerance, andgenes for quality improvements such as yield, nutritional enhancements,environmental or stress tolerances, or any desirable changes in plantphysiology, growth, development, morphology or plant product(s). Forexample, structural genes would include any gene that confers insecttolerance including but not limited to a Bacillus insect control proteingene as described in WO 99/31248, herein incorporated by reference inits entirety, U.S. Pat. No. 5,689,052, herein incorporated by referencein its entirety, U.S. Pat. Nos. 5,500,365 and 5,880,275, hereinincorporated by reference it their entirety. In another embodiment, thestructural gene can confer tolerance to the herbicide glyphosate asconferred by genes including, but not limited to Agrobacterium strainCP4 glyphosate resistant EPSPS gene (aroA:CP4) as described in U.S. Pat.No. 5,633,435, herein incorporated by reference in its entirety, orglyphosate oxidoreductase gene (GOX) as described in U.S. Pat. No.5,463,175, herein incorporated by reference in its entirety.

Alternatively, the DNA coding sequences can affect these phenotypes byencoding a non-translatable RNA molecule that causes the targetedinhibition of expression of an endogenous gene, for example viaantisense- or cosuppression-mediated mechanisms (see, for example, Birdet al., Biotech. Gen. Engin. Rev., 9:207, 1991). The RNA could also be acatalytic RNA molecule (i.e., a ribozyme) engineered to cleave a desiredendogenous mRNA product (see for example, Gibson and Shillito, Mol.Biotech., 7:125, 1997). Thus, any gene which produces a protein or mRNAwhich expresses a phenotype or morphology change of interest is usefulfor the practice of the present invention.

F. DEFINITIONS

In the description and tables herein, a number of terms are used. Inorder to provide a clear and consistent understanding of thespecification and claims, the following definitions are provided:

Allele: Any of one or more alternative forms of a gene locus, all ofwhich alleles relate to one trait or characteristic. In a diploid cellor organism, the two alleles of a given gene occupy corresponding locion a pair of homologous chromosomes.

Backcrossing: A process in which a breeder repeatedly crosses hybridprogeny, for example a first generation hybrid (F₁), back to one of theparents of the hybrid progeny. Backcrossing can be used to introduce oneor more single locus conversions from one genetic background intoanother.

Converted (Conversion) Plant: Plants which are developed by a plantbreeding technique called backcrossing, wherein essentially all of thedesired morphological and physiological characteristics of a lettuceline are recovered in addition to the trait transferred into the varietyvia the backcrossing technique and/or by genetic transformation.

Crossing: The mating of two parent plants.

Cross-pollination: Fertilization by the union of two gametes fromdifferent plants.

Diploid: A cell or organism having two sets of chromosomes.

Emasculate: The removal of plant male sex organs or the inactivation ofthe organs with a cytoplasmic or nuclear genetic factor conferring malesterility or a chemical agent.

Enzymes: Molecules which can act as catalysts in biological reactions.

F₁ Hybrid: The first generation progeny of the cross of two nonisogenicplants.

Genotype: The genetic constitution of a cell or organism.

Haploid: A cell or organism having one set of the two sets ofchromosomes in a diploid.

Linkage: A phenomenon wherein alleles on the same chromosome tend tosegregate together more often than expected by chance if theirtransmission was independent.

Marker: A readily detectable phenotype, preferably inherited incodominant fashion (both alleles at a locus in a diploid heterozygoteare readily detectable), with no environmental variance component, i.e.,heritability of 1.

Phenotype: The detectable characteristics of a cell or organism, whichcharacteristics are the manifestation of gene expression.

Quantitative Trait Loci (QTL): Quantitative trait loci (QTL) refer togenetic loci that control to some degree numerically representabletraits that are usually continuously distributed.

Regeneration: The development of a plant from tissue culture.

Royal Horticultural Society (RHS) color chart value: The RHS color chartis a standardized reference which allows accurate identification of anycolor. A color's designation on the chart describes its hue, brightnessand saturation. A color is precisely named by the RHS color chart byidentifying the group name, sheet number and letter, e.g., Yellow-OrangeGroup 19A or Red Group 41B.

Self-pollination: The transfer of pollen from the anther to the stigmaof the same plant.

Substantially Equivalent: A characteristic that, when compared, does notshow a statistically significant difference (e.g., p=0.05) from themean.

Tetraploid: A cell or organism having four sets of chromosomes.

Tissue Culture: A composition comprising isolated cells of the same or adifferent type or a collection of such cells organized into parts of aplant.

Transgene: A genetic locus comprising a sequence which has beenintroduced into the genome of a lettuce plant by transformation.

Triploid: A cell or organism having three sets of chromosomes.

G. DEPOSIT INFORMATION

A deposit of lettuce line SV3673LD, disclosed above and recited in theclaims, has been made with the American Type Culture Collection (ATCC),10801 University Blvd., Manassas, Va. 20110-2209. The date of depositwas Jul. 3, 2014. Upon issuance of a patent, all restrictions upon thedeposit will be removed, and the deposit is intended to meet all of therequirements of 37 C.F.R. §1.801-1.809. The accession number for thosedeposited seeds of lettuce line SV3673LD is ATCC Accession No.PTA-121365. The deposit will be maintained in the depository for aperiod of 30 years, or 5 years after the last request, or for theeffective life of the patent, whichever is longer, and will be replacedif necessary during that period.

Although the foregoing invention has been described in some detail byway of illustration and example for purposes of clarity andunderstanding, it will be obvious that certain changes and modificationsmay be practiced within the scope of the invention, as limited only bythe scope of the appended claims.

All references cited herein are hereby expressly incorporated herein byreference.

What is claimed is:
 1. A seed of lettuce line SV3673LD, a sample of seed of said line having been deposited under ATCC Accession Number PTA-121365.
 2. A plant grown from the seed of claim
 1. 3. A plant part of the plant of claim
 2. 4. The plant part of claim 3, wherein said part is selected from the group consisting of a pollen, an ovule and a cell.
 5. A lettuce plant, or a part thereof, having all the physiological and morphological characteristics of the lettuce plant of claim
 2. 6. A tissue culture of regenerable cells of lettuce line SV3673LD, a sample of seed of said line having been deposited under ATCC Accession Number PTA-121365.
 7. The tissue culture of claim 6, wherein said tissue culture comprises cells or protoplasts from a plant or plant part selected from the group consisting of embryos, meristems, cotyledons, pollen, leaves, anthers, roots, root tips, pistil, flower, seeds and stalks.
 8. A lettuce plant regenerated from the tissue culture of claim 6, wherein the regenerated plant expresses all of the physiological and morphological characteristics of lettuce line SV3673LD, a sample of seed of said line having been deposited under ATCC Accession Number PTA-121365.
 9. A method of producing lettuce seed, comprising crossing the plant of claim 2 with a second lettuce plant.
 10. The method of claim 9, wherein the plant of lettuce line SV3673LD is the female parent.
 11. The method of claim 9, wherein the plant of lettuce line SV3673LD is the male parent.
 12. An F1 hybrid seed produced by the method of claim
 9. 13. An F1 hybrid plant produced by growing the seed of claim
 12. 14. A method for producing a seed of a line SV3673LD-derived lettuce plant comprising the steps of: (a) crossing a lettuce plant of line SV3673LD, a sample of seed of said line having been deposited under ATCC Accession Number PTA-121365, with a second lettuce plant; and (b) allowing seed of a SV3673LD-derived lettuce plant to form.
 15. The method of claim 14, further comprising the steps of: (c) crossing a plant grown from said SV3673LD-derived lettuce seed with itself or a second lettuce plant to yield additional SV3673LD-derived lettuce seed; (d) growing said additional SV3673LD-derived lettuce seed of step (c) to yield additional SV3673LD-derived lettuce plants; and (e) repeating the crossing and growing steps of (c) and (d) to generate further SV3673LD-derived lettuce plants.
 16. A method of vegetatively propagating a plant of lettuce line SV3673LD comprising the steps of: (a) collecting tissue capable of being propagated from a plant of lettuce line SV3673LD, a sample of seed of said line having been deposited under ATCC Accession Number PTA-121365; and (b) producing at least a first rooted plant from said tissue.
 17. A process of producing a conversion of lettuce line SV3673LD comprising a new trait, the process comprising: (a) crossing a plant of lettuce line SV3673LD, wherein a sample of seed of said line has been deposited under ATCC Accession Number PTA-121365, with a lettuce plant that comprises a new trait to produce progeny seed; (b) harvesting and planting the progeny seed to produce at least one progeny plant of a subsequent generation, wherein the progeny plant comprises the new trait; (c) crossing the progeny plant with a plant of lettuce line SV3673LD to produce backcross progeny seed; (d) harvesting and planting the backcross progeny seed to produce at least one backcross progeny plant; and (e) repeating steps (c) and (d) for at least three additional generations to produce a converted plant of lettuce line SV3673LD, wherein the converted plant of lettuce line SV3673LD comprises the new trait.
 18. A converted lettuce plant produced by the method of claim
 17. 19. A method of producing a plant of lettuce line SV3673LD comprising an added desired trait, the method comprising introducing a transgene conferring the desired trait into a plant of lettuce line SV3673LD, wherein a sample of seed of said line has been deposited under ATCC Accession Number PTA-121365.
 20. A plant produced by the method of claim
 19. 21. A method of producing food comprising: (a) obtaining the plant of claim 2, and (b) collecting leaf tissue from the plant, wherein the leaf tissue is capable of use as food. 